Protein kinases (PKs) are a group of enzymes that regulate diverse, important biological processes including cell growth, survival and differentiation, organ formation and morphogenesis, neovascularization, tissue repair and regeneration, among others. Protein kinases exert their physiological functions through catalyzing the phosphorylation of proteins (or substrates) and thereby modulating the cellular activities of the substrates in various biological contexts. In addition to the functions in normal tissues/organs, many protein kinases also play more specialized roles in a host of human diseases including cancer. A subset of protein kinases (also referred to as oncogenic protein kinases), when dysregulated, can cause tumor formation and growth, and further contribute to tumor maintenance and progression (Blume-Jensen P et al, Nature 2001, 411(6835):355-365). Thus far, oncogenic protein kinases represent one of the largest and most attractive groups of protein targets for cancer intervention and drug development.
Protein kinases can be categorized as receptor type and non-receptor type. Receptor tyrosine kinases (RTKs) have an extracellular portion, a transmembrane domain, and an intracellular portion, while non-receptor tyrosine kinases are entirely intracellular. RTK mediated signal transduction is typically initiated by extracellular interaction with a specific growth factor (ligand), typically followed by receptor dimerization, stimulation of the intrinsic protein tyrosine kinase activity, and receptor transphosphorylation. Binding sites are thereby created for intracellular signal transduction molecules and lead to the formation of complexes with a spectrum of cytoplasmic signaling molecules that facilitate the appropriate cellular response such as cell division, differentiation, metabolic effects, and changes in the extracellular microenvironment
At present, at least nineteen (19) distinct RTK subfamilies have been identified. One RTK subfamily, designated the HER subfamily, includes EGFR, HER2, HER3 and HER4, and bind such ligands as epithelial growth factor (EGF), TGF-α, amphiregulin, HB-EGF, betacellulin and heregulin. A second family of RTKs, designated the insulin subfamily, includes the INS-R, the IGF-1R and the IR-R. A third family, the “PDGF” subfamily, includes the PDGF alpha and beta receptors, CSFIR, c-kit and FLK-II. Another subfamily of RTKs, referred to as the FLK subfamily, encompasses the Kinase insert Domain-Receptor fetal liver kinase-1 (KDR/FLK-1), the fetal liver kinase 4 (FLK-4) and the fins-like tyrosine kinase 1 (flt-1). Two other subfamilies of RTKs have been designated as the FGF receptor family (FGFR1, FGFR2, FGFR3 and FGFR4) and the Met subfamily (c-Met, Ron and Sea). For a detailed discussion of protein kinases, see for example, Blume-Jensen, P. et al., Nature. 2001, 411(6835):355-365, and Manning, G. et al., Science. 2002, 298(5600):1912-1934.
The non-receptor type of tyrosine kinases is also composed of numerous subfamilies, including Src, Btk, Abl, Fak, and Jak. Each of these subfamilies can be further subdivided into multiple members that have been frequently linked to oncogenesis. The Src family, for example, is the largest and includes Src, Fyn, Lck and Fgr among others. For a detailed discussion of these kinases, see Bolen J B. Nonreceptor tyrosine protein kinases. Oncogene. 1993, 8(8):2025-31.
A significant number of tyrosine kinases (both receptor and nonreceptor) are associated with cancer (see Madhusudan S, Ganesan T S. Tyrosine kinase inhibitors in cancer therapy. Clin. Biochem. 2004, 37(7):618-35.). Clinical studies suggest that overexpression or dysregulation of tyrosine kinases may also be of prognostic value. For example, members of the HER family of RTKs have been associated with poor prognosis in breast, colorectal, head and neck and lung cancer. Mutation of c-Kit tyrosine kinase is associated with decreased survival in gastrointestinal stromal tumors. In acute myelogenous leukemia, Flt-3 mutation predicts shorter disease free survival. VEGFR expression, which is important for tumor angiogenesis, is associated with a lower survival rate in lung cancer. Tie-1 kinase expression inversely correlates with survival in gastric cancer. BCR-Abl expression is an important predictor of response in chronic myelogenous leukemia and Src tyrosine kinase is an indicator of poor prognosis in all stages of colorectal cancer.
c-Met, a proto-oncogene, is a member of a distinct subfamily of heterodimeric receptor tyrosine kinases which include Met, Ron, and Sea (Birchmeier, C. et al., Nat. Rev. Mol. Cell. Biol. 2003, 4(12):915-925; Christensen, J. G. et al., Cancer Lett. 2005, 225(1):1-26). The only high affinity ligand for c-Met is the hepatocyte growth factor (HGF), also known as scatter factor (SF). Binding of HGF to c-Met induces activation of the receptor via autophosphorylation resulting in an increase of receptor dependent signaling. Both c-Met and HGF are widely expressed in a variety of organs, but their expression is normally confined to the cells of epithelial and mesenchymal origin, respectively. The biological functions of c-Met (or c-Met signaling pathway) in normal tissues and human malignancies such as cancer have been well documented (Christensen, J. G. et al., Cancer Lett. 2005, 225(1):1-26; Corso, S. et al., Trends in Mol. Med. 2005, 11(6):284-292).
HGF and c-Met are each required for normal mammalian development, and abnormalities reported in both HGF- and c-Met-null mice are consistent with proximity of embryonic expression and epithelial-mesenchymal transition defects during organ morphogenesis (Christensen, J. G. et al., Cancer Lett. 2005, 225(1):1-26). Consistent with these findings, the transduction of signaling and subsequent biological effects of HGF/c-Met pathway have been shown to be important for epithelial-mesenchymal interaction and regulation of cell migration, invasion, cell proliferation and survival, angiogenesis, morphogenesis and organization of three-dimensional tubular structures (e.g. renal tubular cells, gland formation) during development. The specific consequences of c-Met pathway activation in a given cell/tissue are highly context-dependent.
Dysregulated c-Met pathway plays important and sometimes causative (in the case of genetic alterations) roles in tumor formation, growth, maintenance and progression (Birchmeier, C. et al., Nat. Rev. Mol. Cell. Biol. 2003, 4(12):915-925; Boccaccio, C. et al., Nat. Rev. Cancer 2006, 6(8):637-645; Christensen, J. G. et al., Cancer Lett. 2005, 225(1):1-26). HGF and/or c-Met are overexpressed in significant portions of most human cancers, and are often associated with poor clinical outcomes such as more aggressive disease, disease progression, tumor metastasis and shortened patient survival. Further, patients with high levels of HGF/c-Met proteins are more resistance to chemotherapy and radiotherapy. In addition to the abnormal HGF/c-Met expression, c-Met receptor can also be activated in cancer patients through genetic mutations (both germline and somatic) and gene amplification. Although gene amplification and mutations are the most common genetic alterations that have been reported in patients, the receptor can also be activated by deletions, truncations, gene rearrangement, as well as abnormal receptor processing and defective negative regulatory mechanisms.
The various cancers in which c-Met is implicated include, but are not limited to: carcinomas (e.g., bladder, breast, cervical, cholangiocarcinoma, colorectal, esophageal, gastric, head and neck, kidney, liver, lung, nasopharygeal, ovarian, pancreas, prostate, thyroid); musculoskeletal sarcomas (e.g., osteosarcoma, synovial sarcoma, rhabdomyosarcoma); soft tissue sarcomas (e.g., MFH/fibrosarcoma, leiomyosarcoma, Kaposi's sarcoma); hematopoietic malignancies (e.g., multiple myeloma, lymphomas, adult T cell leukemia, acute myelogenous leukemia, chronic myeloid leukemia); and other neoplasms (e.g., glioblastomas, astrocytomas, melanoma, mesothelioma and Wilm's tumor (www.vai.org/met/; Christensen, J. G. et al., Cancer Lett. 2005, 225(1):1-26).
The notion that the activated c-Met pathway contributes to tumor formation and progression and could be a good target for effective cancer intervention has been further solidified by numerous preclinical studies (Birchmeier, C. et al., Nat. Rev. Mol. Cell. Biol. 2003, 4(12):915-925; Christensen, J. G. et al., Cancer Lett. 2005, 225(1):1-26; Corso, S. et al., Trends in Mol. Med. 2005, 11(6):284-292). For example, studies showed that the tpr-met fusion gene, overexpression of c-met and activated c-met mutations all caused oncogenic transformation of various model cell lines and resulted in tumor formation and metastasis in mice. More importantly, significant anti-tumor (sometimes tumor regression) and anti-metastasis activities have been demonstrated in vitro and in vivo with agents that specifically impair and/or block HGF/c-Met signaling. Those agents include anti-HGF and anti-c-Met antibodies, HGF peptide antagonists, decoy c-Met receptor, c-Met peptide antagonists, dominant negative c-Met mutations, c-Met specific antisense oligonucleotides and ribozymes, and selective small molecule c-Met kinase inhibitors (Christensen, J. G. et al., Cancer Lett. 2005, 225(1):1-26).
In addition to the established role in cancer, abnormal HGF/c-Met signaling is also implicated in atherosclerosis, lung fibrosis, renal fibrosis and regeneration, liver diseases, allergic disorders, inflammatory and autoimmune disorders, cerebrovascular diseases, cardiovascular diseases, conditions associated with organ transplantation (Ma, H. et al., Atherosclerosis. 2002, 164(1):79-87; Crestani, B. et al., Lab. Invest. 2002, 82(8):1015-1022; Sequra-Flores, A. A. et al., Rev. Gastroenterol. Mex. 2004, 69(4)243-250; Morishita, R. et al., Curr. Gene Ther. 2004, 4(2)199-206; Morishita, R. et al., Endocr. J. 2002, 49(3)273-284; Liu, Y., Curr. Opin. Nephrol. Hypertens. 2002, 11(1):23-30; Matsumoto, K. et al., Kidney Int. 2001, 59(6):2023-2038; Balkovetz, D. F. et al., Int. Rev. Cytol. 1999, 186:225-250; Miyazawa, T. et al., J. Cereb. Blood Flow Metab. 1998, 18(4)345-348; Koch, A. E. et al., Arthritis Rheum. 1996, 39(9):1566-1575; Futamatsu, H. et al., Circ. Res. 2005, 96(8)823-830; Eguchi, S. et al., Clin. Transplant. 1999, 13(6)536-544).
Despite the important/causative roles that the c-Met pathway plays in the above described human diseases including cancer, there are no c-Met inhibitors or antagonists that are currently available for treating these human disorders that associate with abnormal HGF/c-Met signaling. Therefore, there is a clear unmet medical need to develop new compounds as inhibitors of c-Met and other kinases. The compounds, compositions, and pharmaceutical methods provided herein help meet this need.